Water-soluble polyelectrolyte nanocapsules can be synthesized by vesicular
or emulsion polymerization via core-shell latexes. These particles show a r
eversible pH- and ionic strength-dependent swelling transition causing a co
nsiderable increase (decrease) of their radius. During this transition gate
d pores are opened (closed) in spherical polymer shells, which enable free
molecular exchange between the interior of the hollow sphere and the bulk m
edium. This pH-switchable control of the permeability of the polyelectrolyt
e envelopes can be used to trigger the release of encapsulated materials fr
om their central cavity.